The invention relates to a reciprocation motor, and, more particularly, to means capable of detecting the rotation angle of a reciprocating rotor accurately.
A reciprocation motor is already known in which control of the rotation angle of a rotor can be freely made. A transverse sectional view of this prior art reciprocation motor is shown in FIG. 14. Rotor 1 is a cylindrically-shaped magnet having two poles spaced apart in a radial direction thereof and comprises a pair of half-cylindrical magnets. One end of the magnet is formed so as to be an N pole, and other end is formed so as to be an S pole. FIG. 15 shows a view where the reciprocation motor of FIG. 14 is spread out in a plan view. Driving coils 5a and 5b are wound equally on coil board 3. Magnetic sensor 7 is centrally fixed inside the driving coil 5b on coil board 3. Magnetic sensor 7 may comprise, for example, a Hall element capable of converting magnetic flux to voltage.
Next, the operation will be described. When current flows through driving coils 5a and 5b, torque occurs between driving coils 5a, 5b and the magnet of rotor 1. When current is maintained at a predetermined value, rotor 1 stops. When driving coils 5a and 5b are connected in series, and alternating current flows through time, it is possible to cause reciprocating motion through 180 degrees. Although two driving coils 5a and 5b are shown in FIG. 15, the reciprocating range can be determined freely using one or plural driving coils. When rotor 1 reciprocates as shown in FIG. 16, an output shown in FIG. 17 is obtained from magnetic sensor 7. It is possible to obtain an output from magnetic sensor 7 nearly in proportion to the magnetic field. Therefore, it is possible to control the rotor 1 to stop at a desired position by adjusting the current of driving coil 5 so as to make the output signal from magnetic sensor 7 a predetermined value. It is possible to control reciprocating motion through a desired angular range by inputting an alternating signal from an oscillator, not shown, to driving coil 5.
Thus, by forming magnetic sensor 7 centrally at the inside of driving coil 5b this makes it possible to control current of the driving coil and to detect the position (angle) of rotor 1.
The prior art reciprocating motor is influenced by not only magnetic flux of magnet of rotor 1 but also magnetic flux of current flowing through driving coil 5b because the magnetic sensor 7 is formed centrally inside driving coil 5b. Therefore, there is a possibility that the position detecting accuracy of the rotor 1 is diminished.
In order to solve the prior art problem noted above, an object of the present invention is to provide a reciprocating motor capable of detecting the rotation angle of the rotor accurately.